1. Field of Invention
The invention relates to surface controlled subsurface safety valves. More particularly, the invention relates to electro-hydraulic actuation systems for such valves.
2. Prior Art
Surface controlled subsurface safety valves have been used for many years to prevent such occurrences as "blowouts" and other dangerous well conditions. Safety valves are designed so that if they fail, they fail in a safe position so that upon a break in the hydraulic fluid system, conventionally supplied at the surface and extended in a small diameter high pressure tubing line downhole, the power spring in the safety valve closes the flapper of the safety valve. The power spring must be able to lift the hydraulic column to the surface. This requires very strong springs and consequently, high opening pressures for valves set very deeply within the earth{character pullout}s crust.
More recently, electromechanical actuators have been conceived employing electrically actuated mechanical means to open the flapper. The electromechanical systems are extremely effective for installations in which they are specified but different wells have different requirements and the art is still in need of other types of actuating systems.